Configure via admin panel which INSPIRE conformance classes to run

Currently it is configured in xml file https://github.com/geonetwork/core-geonetwork/blob/master/services/src/main/resources/config-spring-geonetwork.xml#L90-L119 which conformance classes are implemented under which conditions.

A suggestion would be to create a more dynamic situation where this is configurable from the https://vanilla.geocat.net/geonetwork/srv/eng/admin.console#/metadata/schematron validation admin screen.

The screen could actually query the selected ETF instance to retrieve available conformance classes and let a user select the relevant conformance classes. To offer a certain conformance classes can also be configured to be evaluated with an xpath expression (similar to current schematron configuration).

Start with services/src/main/resources/config-spring-geonetwork.xml#L90-L119 and inspect the validation admin screen at /admin.console#/metadata/schematron. Determine how the selected ETF instance exposes conformance classes and how current XPath-based Schematron conditions are represented. Done means users can select available INSPIRE conformance classes and configure their evaluation conditions from the admin screen instead of the XML file.

Written by the indexing model from the issue text.